The increases or decreases in the market value of unsold securities whose gains or losses were included in earnings, and which, were not separately or otherwise categorized as trading, available-for-sale, or held-to-maturity.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 28

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3602-108585

Name:	us-gaap_UnrealizedGainLossOnSecurities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Fair Value Measurements (Details Textual) (USD $)	3 Months Ended			3 Months Ended
Fair Value Measurements (Details Textual) (USD $)	Mar. 31, 2013	Dec. 31, 2012 U.S. Treasuries [Member]	Mar. 31, 2013 Quoted prices in active markets for identical assets (Level 1) [Member] U.S. Treasuries [Member]	Mar. 31, 2013 Maximum [Member]	Mar. 31, 2013 Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments held to maturity measured on non recurring basis		$ 0	$ 3,000,000
Short-term investments minimum maturity period, in days				1 year	90 days
Fair Value Measurements (Textual) [Abstract]
Unrealized gain and losses	$ 0